Color photography



latentecl Dec. 15, 1942" UNITED STATES COLOR- PHOTOGBAPHY Burt H. Carroll, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application April 8, 1941, Serial No. 387,450. In Great Britain April 9, 1940 Claims.

This invention relates to color photography and particularly to an improved material for the bleach-out method of color photography.

Processes of color photography are known which make use of uniformly dyed silver'halide emulsions, the colored image being formed by destroying'the dye in the regions of a silver or silver salt image; The dye incorporated in the gelatin or emulsion may possess a color which is complementary to that of the light which the sensitive emulsion is intended to record or may be such as to transmit it freely.

This invention relates to processes of the former type in which the dye incorporated in the gelatin i5 630 millimicrons to 600 millimicrons has been or emulsion is complementary in color to that of the light which the emulsion is intended to record. In such processes the dye which is used has its light absorption maximum at a wave length which is substantially identical with the maximum sensitivity of the emulsion in which the dye is incorporated. There is, therefore, a loss in sensitivity because the maximum absorption of the dye corresponds to the region of maximum sensitivity of the emulsion. This inherent limitation on speed, combined with desensitizing action of the coloring dyes, which is usually found in practice, limits the process to 'use with printing materials and requires relatively sensitive emulsions in order to secure a working sensitivity adequate for enlarging.

It is, therefore, an object of the present invention to providea material which" retains the inherent advantage of this type of bleach-out process, affording direct color positives, while increasing the speed of the material. Another ob- ,iect is to provide a novel method of coloring emulsion layers for the bleach-out process of'color photography. 'A still further'object is to provide a method of increasing the effective sensitivity of silver halide emulsion layers used in the bleachout process of color photography. Other objects will appear from the following description of my invention.

These objects are accomplished by treating dyes suitable for use in the bleach-out method of color photography so that their absorption maxima are shifted from the region of maximum sensitivity of the layers in which they are incorporated, and after exposure, reconvertingthe dyes to dyes having the proper colors for image dyes. This is ac complished by forming in the photographic layer a dye derivative by treatment of a dye with-a metallic salt, preferably an alkaline earth metal salt of an inorganic acid, prior to exposure and-subsequently restoring the dye to a 'form having the 55 proper light absorption and transmission characteristics for an image forming dye.

When the dyes used in the photographic. layers are treated with metallic salts according to the present invention, the metallic derivatives so formed have a color which differs from that of.

the original dye by an amount sufllcient' to cause an appreciable reduction in the light absorption of the dye in the region which the emulsion isin- 1o tended to record and, therefore, an increase inv the elfective sensitivity of the layer is obtained. The change in the light absorption of the dye need not be excessive. For example, a change in the absorption maximum of a blue-green dye from found to increase the effective speed ofthe layer in which it is incorporated six times or more.

' Any suitable dyeswhlch give a metallic derive tive, preferably an insoluble derivative, on treatpolyazo' acid dyes.

The metallic salts are preferably alkaline earthsuch as cobalt or nickel salts or salts of complex cations containing metals. Generally, those metallic salts are preferred which change the light absorption maximum of the dye to a shorter wave length since most absorption bands fall ,ofl' more sharply on the long wave length side of the maxi mum. After exposure of the dyed layer to forlnanirnsoluble derivative or precipitated in the layer by double decomposition of the dye derivative. Some metals may be partially or wholly removed 40 from the dye during development of the layer in the form of their carbonate or sulfites which may be slightly soluble, but it is generally necessary;

to take special steps to insure that the whole of the metal" is removed from the layer or suitably precipitated in the layer. For example, the metal may be fully removed from the layer during bleaching of the dye by using strong acid baths and subjecting the layer to prolonged washing or the metal may be removed from the dye by precipitation within the layer, by treatment with a 7 bath containing a soluble salt such as a sulfate,

which forms an insoluble compound of the metal,

preferably a colorless compound. If desired, such' the baths used for processing the layer to a colored The following dyes are specifically suitable for image. use according to my invention:

The proposed method may be applied to multi- The following blue-green dyes color photographic processes, for example, a

Pontamine Fast Green BL three color process, using photographic elements 5 solophenyl Fast Blue Green comprising a plurality of differentially colorsensitive layers coated on a single support. In. (The dyes of this type are described in Richard a three-color process, for example, a sensitive U. S. Patent 1,829,673, granted October 27, 1931.)

element may comprise a gelatino silver halide They are believed to have the following formula 1 emulsion sensitized to red light and dyed unior substantially similar constitutions:

' 1 5 H a C N=N N=N V N=N gaoi mum SOSNI OaNa s'olNa v NQLO formly with a blue-green, a gelatino-silver halide The dyes having the following formulas:

and shade at any convenient stage in the proc- O 'essing provided that they remain in their converted and shifted absorption form during exon some OzNa I emulsion sensitive to'green light and dyed unit 00,131, on

formly with a magenta dye, and a not-especially l color-sensitized gelatino-silver halide emulsion Q layer dyed uniformly with a yellow dye. One or so'Na I H, 1

more of three image-forming dyes should be such r that they form metallic salts of a different shade 7 some Soil y when treated with suitable metallic salts. Pref- (This dye is obtained by diazotizing metanllio erably the diiference in the absorption maximum acid and coupli in d medium with -hflDhcf the dye and its metallic salt should be at least thY am i-S acid. diazotizini e result- 20 millimicrons and preferablyfrom to 50 ing dye and coupling in 0 11 medium with 2- millimicrons. After'exposure of the element to 30 Y-1* D Y u ac d, d amform an image or images, a silver image or im-' tilin th resulting dye and l p ing inalkalino 1 ages are produced in the layers by primary or medium wi 2 -amino-5-naphthol-7-sulfonio reversal development and a colored image or acid. The finished dye as e dium salt orreimages formed by decolorizing or destroying one PO d the ebOVe Structural ula.) or more of the dyes in accordance with well known 241 some 7 a methods such as those described in Christensen I U. s. Patent 1,517,049, granted November 25, arr-Q 1924, and Seymour U. S. Patent 2,184,022 granted December 19, 1939. After formation of the col- SOINI ored image or images. the'remalning silver and 4 silver halide in the layers may be removed in any suitable manner. 248 some The dyes may be restored to their original form posure.

Dyes which I may use include blue to bluegreen dyes'having the following groupings press 0H ent in their molecules: e on 0H R1 N=i-z N=N g mo ommo om R, 411' 7 NE I 011 f. V Y 'OH CH: CH: NH: or

I I R1 7 N=N N=N I 0 mo some mo om. =N R Numbers in the nrstcolumn are those given to OH I these dyes in Schultz-Lehmann, Farbstofltabell. Y Y "7th edition. e where I v e I v .65 4 1 on 0cm eon; e R.'=arylamine v N=N arylradical containing an & Broup I R1=H alkyl, alkoxy 5 Rz=either hydrogens or a fused benzene ring 05 (forming naphthalene). on eon, com The dyes must also contain one or more saltforming groups. such as suifonic acid groups, and Nlo so N 0 may contain other substituent groups. -78 r 9 v Nmon ocm OCH: NH:

N= N=N oiNfl soim 610 s can OH on N=N =N s QNa N80: Nil-O,

(This dye is prepared by diazotizing 1 mole of l-amino-8-naphthol-3,fi-disulfonic acid and coupling it in acid medium with 1 mole of a-naphthylamine, again diazotizing and coupling in alkaline medium with 1 mole of 1-amino-8-naph- I thol-3,6-disulfonic acid.) 7 t The absorption maxima of the above dyes may be shifted toward the shorter wave length by converting the dyes to their barium salts. They may 3 strongly acid bleach baths and long washing times areused.

lilxcmplez 1 1 No. 307) there is added an excess of cobalt hexbe usedto color the red sensitive layer of a multi- 1 layer element. I

Benzo Light Yellow RL (Schultz Lehmann Farbstoiitabellen, 7th edition, No. 307). :This dye is believed to have the following structural formula:

The above dye may be converted to a form having'its absorption maximum shifted toward shorter wave lengths by treatment with cobalt hexamino nitrate to form a cobalt complex salt.

My invention may be further illustrated ,by the following specific examples:

Example 1 To a red-sensitized emulsion dyed with Ponta; mine Fast Green 53L or Solophenyl Fast Blue- Green BL there is added a water-soluble barium salt such as barium nitrate or barium acetate in line earth metal salt of a polyazo dye, the sodium an amount of the order of the weight or the dye,

that is, an amount in excess of that necessary to combine with the dye. Since the dye exists as its sodium salt an excess of barium salt is necessary in order to displace the sodium ions by mass action, the barium salts of the dye being slightly soluble. The dye is thus changed from On exposure and processing the layer, the barium is first removed as carbonate or sulflte during development. The dye then reverts to its original color. During bleaching of the layer. the barium will be permanently removedii amino nitrate. The dye becomes nearly colorless by formation of the corresponding salt. on exposure and processing of the layer, the original color of the dye is restored by elimination of the. cobalt complex.

I realize that some of the dyes used as examples in the present specification have previously been described tor use in photographic emulsion layers. However, I claim as novel the discovery that the absorption maxima of these dyes may be shifted to a region outside the region of maximum sensitivity of an emulsion layer in which they are to be incorporated and the efiectivesensitvity oi the layer thereby increased.

I claim:

' 1. A light-sensitve silver halide layer for th bleach-out process of color photography, effectively sensitive to only one of the primary colors, said layer being uniformly colored witha salt of a polyazo dye selected from the group consisting aialkaline earth metal salts, nickel, and cobalt, the sodium salt of said dye having an absorption maximum at substantially the sensitvity maximum of the layer, but the. first mentioned salt having a light absorption maximum at a sub-- tively sensitive to only one of the primary colors,

said layer being uniformly colored with an alkasalt 01 said dye having an absorption maximum at substantially the sensitivity maximum oi. the

layer, but the alkaline earth metal salt having a light absorption maximum at a substantially lower wave length than the sensitivity maximum of said' layer. said alkaline earth metalsalt of v salt of a polyazo dye, the sodium salt of said dye having an absorption maximum at substantially the sensitivity maximum 10! the-layer, but'the alkaline earth metal salt having a light absorption'maxium at a substantially lower wave length than the sensitivity maximum of said layer, said alkaline earth metal salt 01 said dye being con-' vertible into a term having an absorption maximum at substantially the sensitivity maximum of the layer.

4. A light-sensitive silver halide layer for the bleach-out-process oi color photography eflectively sensitive to only one of the primary colors,

said layer being uniformly colored with a barium salt of a polyazo dye, the sodium salt of said dye having an absorption maximum at substantially the sensitivity maximum oi the layer but the barium salt having a light absorption maximum at a substantially lower wave length, and

halide. emu] said barium salt of said dye being convertible after exposure of the layer, to a form having an absorption maximum at substantially the sensitivity maximum of the layer.

5. A lightwsensitive gelatino-silverhalide layer for the bleach-out process of color photography colored with the barium salt of a dye having the following formula:

X OH Y uniformly colored with a cobalt complex salt of the dye having the following structural formula N=NOSOaNa CH:

said cobalt salt having a light absorption maximum not corresponding to the sensitivity maximum of the silver halide layer, but the sodium salt of the dye having a light absorption maximum at substantially the sensitivity maximum of the layer. I

9. The method of increasing the effective sensitivity of a silver halide photographic layer used in the bleach-out process of color photography, which comprises converting an azo dye having a light absorption maximum in the region which 'said layer records, into a salt of said dye selected from the group consisting of alkaline earth metal salts, nickel and cobalt, the sodium salt of said for thebleach-out process of color photography colored with the barium salt 01 a dye having the following formula:

- OH IIIH:

1 m, on

where Y=hydrogen, methyl, methoxy; and from 1 to 2 Zs of each Iiaphthyl radical are the barium salt of sulfonic acid, the remaining Zs being hydrogen, said barium salt having a light absorption maximum not corresponding to the sensitivity maximum. of the silver halide layer, but the sodium salt 01 the .dye having a light absorption maximum at substantially the sensitivity maximum of the layer.

7. A light-sensitive gelatino-silver halide layer for the bleach-out process of color photography uniformly colored with the barium salt of Pontamine Fast Green 53L, said barium salt having a light absorption maximum not corresponding to the sensitivity maximum of the silver halide I layer, but-the sodium salt of the dye having a light absorption maximum at substantially the sensitivity maximum of the layer.

8. A light-sensitive gelatino-silver halide layer for the bleach-out process of color photography dye having an absorption maximum at substantially the sensitivity maximum of the layer but said first mentioned salt having a light absorption maximum in a region of substantially lower wave-length and incorporating said salt in said emulsion layer. v

10. A light-sensitive silver halide layer for the silver bleach-out process ofcolor photography colored with the .barium salt of a dye selected from the group consisting oi dyes having the following structure:

it on R Ill on x where R-is selected from the class consisting of hydrogen, alkyl, and alkoxy groups; x is selected from the class consisting of hydrogen, amino, and hydroxyl groups; Y is selected from the class consisting of arylamino and azo groups; and the naphthol nucleus contains at least one sulfonic acid radical capable of forming said'barium salt,

said barium salt having a light-absorption maximum not corresponding to thesensitivity maximum of the silver halide layer, but the sodium salt of the dye having a light-absorption maxi-v mum at substantially the. sensitivity maximum of the layer.

BURT H, CARROLL. 

